Cerebrovascular (CV) disease is the third leading cause of death in the U.S. and about one-quarter of the CV deaths are due to ruptured intracranial aneurysms (IA). Of those that survive rupture, more than half are left with neurological deficits. Elective surgery and treatment prior to rupture are very effective in preventing morbidity and mortality. Early identification of individuals susceptible to IA would therefore greatly enhance our ability to prevent most serious outcomes. Preliminary analysis of a genome scan of 49 affected sib pairs has been completed. Several candidate regions (one with lod score > 2.5) have been implicated. We are currently genotyping additional markers in these candidate regions on the original 49 pairs and an additional set of pairs in an attempt to confirm linkage to one or more of these regions.